JP2011223394A - Node and wireless communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce concentration of traffic on a particular relay node in a multi-hop, wireless communication system.SOLUTION: The present invention relates to a node for multi-hop, wireless communication. The node includes: means to calculate a link cost value by transmitting and receiving control packets to and from neighboring nodes, means to calculate a path cost for a target node; means to monitor each child node for the number of its downstream nodes; and means to generate control information so as to adjust the number of downstream nodes of a child node by modifying link cost information and/or path cost information according to the monitored number of downstream nodes of the child node and inserting the link cost information and/or the path cost information into the control information.

Description

  The present invention relates to a node and a wireless communication system, and can be applied to, for example, a wireless communication system that performs multi-hop wireless communication between nodes.

  Conventionally, as a routing process in a wireless communication system that performs multi-hop wireless communication between nodes, there is a technology described in Non-Patent Document 1 standardized by the ZigBee (registered trademark) alliance.

  In the routing method described in Non-Patent Document 1, the start node of the route floods RREQ (route request) and transmits it to the entire network, and the end node of the route transmits RREP (route reply) to the start node by unicast. Thus, a path of the node between the start point and the end point is formed (refer to “3.6.3.5” of Non-Patent Document 1). At this time, each frame of RREQ and RREP has a path cost field (refer to “3.4.1, 3.4.2” of Non-Patent Document 1), and the link of each link between the start point and the end point A value obtained by adding all the costs (values indicating the quality of the link) is described in this field, so that the highest quality (ie, the one with the lowest path cost) can be selected from a plurality of routes. ing.

  Although this method can create a route between any two nodes, the Many to One method considering 1-to-n communication between a sink node and a plurality of nodes is also described in Non-Patent Document 1, and Many to Even in the One method, the creation of the upstream route to the sink node is almost the same procedure. In this way, a method of selecting a route with the smallest value obtained by adding the link costs as the best route is widely used in the routing of the wireless multi-hop network.

  In Non-Patent Document 1, the link cost is calculated from an LQI (Link Quality lndicator) value when an RREQ command is received. As another method for calculating the link cost more accurately, there is a method in which the node periodically transmits a control packet (Hello packet) and actually measures the reception rate of the control packet to obtain the link cost. In the case of this method, the result of measuring the reception rate of Hello packets from other nodes that can communicate directly (hereinafter referred to as “neighboring nodes”) is described in the Hello packet transmitted by itself and notified to neighboring nodes. Thus, it is possible to know how much the transmitted Hello packet has been transmitted to the other party, and it is possible to know the bidirectional link quality for each link.

ZigBee Standards Organization, “ZigBee Specification Revision 17 (ZigBee Document O53474r17)”, [Online], INTERNET, [March 20, 2010 search], <http: //www.zbsigMG.00 -053474r17_Japanese_081209.pdf>

  FIG. 7 is a block diagram showing a configuration example of a wireless communication system that performs conventional wireless multi-hop communication.

  In the wireless communication system shown in FIG. 7, eight nodes N-0 to N-7 are arranged. In FIG. 7, nodes connected by solid lines or dotted lines are directly communicable nodes, and the numbers attached to the solid lines or dotted lines connecting the nodes indicate the link costs between the nodes. For example, the link cost between the node N-1 and the node N-0 is 1, and the link cost between the node N-3 and the node N-1 is 1. In FIG. 7, the numbers given to the respective nodes N indicate the path costs required for each node N to reach the node N-0. For example, the path cost value at the node N-1 is 1.

  In a routing method such as the technology described in Non-Patent Document 1, when a route connecting a start node and an end node is viewed alone, a good route (a route with a low path cost) can be selected. In the wireless communication system as shown in FIG. 7, when considering traffic in which each of the nodes N-1 to N-7 transmits data to the node N-0, the node N-3 to the node N-0. When the route is formed, the node N-1 relays the data of the nodes N-4, N-5, and N-6 even though the route via the node N-1 having a low path cost is better as the route. However, node N-2 relays only one node N-7, and the route via node N-2 is selected from the viewpoint of avoiding traffic concentration Sometimes it is better. In many cases, such a small scale as shown in FIG. 7 is not a big problem, but when data is collected by constructing a network with hundreds of nodes, such concentration of traffic becomes a problem. It is also important to avoid a case where a node exceeding the processing capability of the node N-1 is connected downstream of the node N-1.

  Therefore, a node and a wireless communication system that can suppress the concentration of relay traffic to a specific node are desired.

  In a first aspect of the present invention, in a node that performs multi-hop wireless communication, (1) a neighboring node capable of direct wireless communication, control information transmission / reception means that transmits / receives a control packet having control information, and (2) control information transmission / reception A link cost calculating means for calculating a link cost value of a link with each neighboring node according to the state of transmission / reception of control information by the means, and (3) reaching the target node when transmitting a packet to the target node. Path cost calculation means for calculating a path cost value until the completion of the processing, and (4) downstream node monitoring means for monitoring the number of downstream nodes for each of the child nodes of the node on the route to the target node. (5) The control information transmitting / receiving means generates control information to be transmitted, and the link cost calculating means includes the control information to be generated. Insert link cost information based on the issued link cost value and / or path cost information based on the path cost value calculated by the path cost calculation means, and further according to the number of downstream nodes of each child node, Control information creating means for adjusting the number of downstream nodes of each child node by adjusting the contents of link cost information or path cost information to be inserted into the created control information.

  According to a second aspect of the present invention, in the wireless communication system having a plurality of nodes performing multi-hop wireless communication, the node of the first aspect of the present invention is applied to a part or all of the nodes constituting the wireless communication system. And

  ADVANTAGE OF THE INVENTION According to this invention, the concentration of the relay traffic to a specific node can be suppressed in the radio | wireless communications system which performs multihop radio | wireless communication.

It is the block diagram shown about the functional structure of the node which concerns on 1st Embodiment. It is the block diagram shown about the whole structure of the radio | wireless communications system which concerns on 1st Embodiment. It is explanatory drawing shown about the state by which the link cost was adjusted in the radio | wireless communications system which concerns on 1st Embodiment. It is the block diagram shown about the whole structure of the radio | wireless communications system which concerns on 2nd Embodiment. It is the block diagram shown about the functional structure of the node which concerns on 2nd Embodiment. It is explanatory drawing shown about the state by which the path cost was adjusted in the radio | wireless communications system which concerns on 2nd Embodiment. It is the block diagram shown about the whole structure of the conventional radio | wireless communications system.

(A) First Embodiment Hereinafter, a first embodiment of a node and a wireless communication system according to the present invention will be described in detail with reference to the drawings.

(A-1) Configuration of the First Embodiment FIG. 2 is a block diagram showing the overall configuration of the wireless communication system 1 of the first embodiment.

  As shown in FIG. 2, eight nodes 10-0 to 10-7 are arranged in the wireless communication system 1.

  For example, FIG. 2 illustrates a case where each of the nodes 10-1 to 10-7 transmits data to the node 10-0 by multi-hop communication.

  Further, FIG. 2 shows that the nodes 10 connected by a solid line or a dotted line can directly communicate with each other.

  Next, the internal configuration of each node 10 will be described.

  FIG. 1 is a block diagram showing a functional configuration of each node 10.

  The node 10 includes a link cost determination unit 11, a link cost table 12, a downstream node management unit 13, a load balance determination unit 14, a link cost notification unit 15, a path cost table 16, and a path cost notification unit 17.

  For example, the node 10 installs a wireless communication program for realizing the functional configuration shown in FIG. 1 in a node (communication device) having an interface that performs wireless communication and a processor that performs communication processing and data processing. You may build by.

  The link cost determination unit 11 receives a control packet (for example, a Hello packet) from a node 10 (neighboring node) capable of direct communication (for example, a reception success rate and a radio wave reception intensity when the control packet is received). Etc.), the link cost value for packet reception from each neighboring node is calculated and stored in the link cost table 12 as the link cost value on the receiving side for the target link. Further, when a packet having link cost information (details will be described later) transmitted by the link cost notifying unit 15 of the neighboring node is received, the link cost value of the transmitting side for the neighboring node from itself is described in the link cost information. In the case where it is described, the link cost value is stored in the link cost table 12 as the link cost value on the transmission side of the target link.

  The link cost determination means 11 calculates a link cost value that comprehensively determines the result when both the transmission side link cost value and the reception side link cost value are known for a certain neighboring node, Save in the link cost table 12. Although this calculation method is not limited, a method of taking an average or a method of adopting a worse value may be employed. The method for calculating the link cost value by the link cost determining means 11 is not limited. For example, a method using a mechanism for periodically transmitting a control packet such as a Hello packet, an LQI of other data packets, etc. There is a simple calculation method using it. Further, only one of the transmission side link cost value or the reception side link cost value may be used for the calculation of the link cost value in the link cost determination means 11.

  The link cost table 12 stores information such as the link cost value determined by the link cost determination unit 11 for each target neighboring node. The link cost table 12 includes a link cost value on the reception side, a link cost value on the transmission side, and a link cost value determined by combining them for the links of the neighboring nodes.

  In FIG. 2, the numbers attached to the dotted lines or solid lines connecting the nodes indicate the link costs determined between the nodes 10. In FIG. 2, the link cost calculated in each of the two nodes 10 connected by the dotted line or the solid line is illustrated as being the same.

  The path cost table 16 stores the contents of the path cost information received from neighboring nodes for each neighboring node of the transmission source. For example, the path cost table 16 may be stored as a set in which identification information such as addresses of neighboring nodes and the received path cost information are associated with each other.

  The path cost information stored in the path cost table 16 includes information on the target node 10 (for example, identification information such as address information) and information on the path cost value up to the target node 10. . For example, in the case of the one-to-n route between the node 10-0 and the other node 10 in FIG. 2, if it is determined in advance that the path cost is for the node 10-0, The description of “node information” can be omitted.

  Further, since the path cost table 16 and the link cost table 12 are one of attribute values for the addresses of neighboring nodes, they may be managed together as the same table. In the path cost table 16, such information on neighboring nodes may be managed collectively as a neighbor table in the same manner as existing wireless communication devices.

  Then, the node 10 uses the contents of the path cost table 16 and the link cost table 12 to select a route when transmitting a packet to the node 10 that is a packet transmission target. For example, the node 10 refers to the contents of the path cost table 16 and the link cost table 12 to select a path with the smallest path cost value to the node 10 that is a packet transmission target, and on the selected path, The node 10 as the first transfer destination is selected as the parent node.

  In the wireless communication system 1, each node 10 performs route selection for the node 10-0 as a packet transmission target and determines a parent node. As a result, a tree-type network as shown in FIG. Is logically formed.

  The downstream node management unit 13 manages a node existing downstream from the node 10. Here, the downstream node indicates the node 10 to which the node 10 relays a packet. For example, in the example of FIG. 2, the node 10-1 is the node 10 at the time of packet transmission to the node 10-0. −4, 10−5, and 10−6, when relaying packets sent from the node 10−1, the downstream nodes of the node 10-1 are the node 10−1, the nodes 10−4, 10−5, and 10−6. . As a method of grasping the downstream node of the node 10-1 in the downstream node management means 13 of the node 10-1, the nodes 10-4, 10-5, and 10-6 send packets to the node 10-0. Since the node 10-1 always relays the packet when sending it, the source node of the packet is recorded as the downstream node. The node 10 that has transmitted a packet for performing data transmission or the like to the node 10-1 is also a downstream node.

  That is, in the case of FIG. 2, when each node 10 transmits a packet to the node 10-0, all the nodes are downstream nodes when viewed from the node 10-0. In addition, for each downstream node, record which neighboring node is downstream of the target downstream node. For example, how far downstream (how many hops the node 10-6 is downstream from the node 10-0) However, it can be determined by the node 10-0 that the transmission to the node 10-0 has passed through the node 10-1 from the contents of the header information of the packet.

  For example, in the node 10-0, the node 10-6 exists downstream, and the downstream node management unit 13 records which node 10 is transmitted to itself. It turns out that it is 1 downstream. Such management can be performed for any packet as long as the destination and source addresses are described in the packet header. However, when a routing method such as source routing is used, all the nodes that are routed at the time of relaying are held as a table, and may be managed as one table together with the table.

  As described above, in the downstream node management unit 13, the number of downstream nodes for each of the target nodes 10 for each of the child nodes capable of direct wireless communication of the node 10 on the path to the target node 10. To figure out.

  Note that the downstream node management means 13 may delete the record relating to the downstream node for which no packet has been generated for a predetermined time. Further, in the downstream node management means 13, the node 10 may be included in the downstream node or may not be included, but the latter is adopted in this embodiment.

  Further, when a downstream node located downstream of a certain child node as viewed from the node 10 changes the connection downstream of another child node, the downstream node management means 13 of the node 10 The previous record relating to the downstream node may be erased and re-recorded as belonging to another child node based on the latest received packet information.

  Based on the result of the downstream node management unit 13, the load balance determination unit 14 determines to perform adjustment so that the number of downstream nodes in its neighboring nodes (directly communicable child nodes) is optimized. The determined content is reflected in the operation of the link cost notification means 15.

  As the adjustment operation of the load balance determination unit 14, when it is assumed that the processing capability of each node 10 is the same, it is determined that the adjustment is performed so that the number of downstream nodes passing through each neighboring node becomes the same.

  For example, in FIG. 2, when the node 10-3 is excluded, the downstream nodes of the node 10-0 are the nodes 10-1, 10-2, 10-4, 10-5, 10− when the packet is transmitted to the node 10-0. 6 and 10-7, and the neighboring nodes are nodes 10-1 and 10-2.

  The downstream nodes that pass through the node 10-1 are the nodes 10-1, 10-4, 10-5, and 10-6, and the downstream nodes that pass through the node 10-2 are the nodes 10-2 and 10-7. Suppose that

  In this case, in the node 10-0, the number of downstream nodes of the node 10-1 is “4”, and the number of downstream nodes of the node 10-2 is recognized as “2”. In this case, since the number of downstream nodes of the node 10-1 is large, in order to reduce this, the link cost notifying unit 15 is notified that the link cost with the node 10-1 needs to be adjusted.

  In addition, when the capacity of the node 10-1 is exceeded (for example, when the number of downstream nodes exceeds a predetermined threshold), it indicates that the number of downstream nodes passing through the node 10-1 cannot be increased any more. Information may be further notified.

  In addition, when the processing capability for each node 10 is different, the load balance determination unit 14 may adjust the number of downstream nodes so that it corresponds to the processing capability.

  The link cost notifying unit 15 inserts information recorded in the link cost table 12 into a control packet (for example, a Hello packet) as link cost information and notifies the neighboring nodes. At this time, if there is a notification of adjustment from the load balance determining means 14, it is notified accordingly.

  For example, if the node 10-1 and the node 10-2 exist in the vicinity of the node 10-0 and the link costs are “1” and “2”, respectively, the node 10− The node 10-0 transmits a packet of link cost information including information that the link cost value with 1 is “1” and the link cost value with the node 10-2 is “2” to the neighboring nodes. At this time, when the number of nodes passing through the node 10-2 is increased by the node 10-0 and the number of nodes passing through the node 10-2 is increased, according to the number of downstream nodes passing through the neighboring nodes, The link cost information adjusted so as to increase the link cost value with the node 10 whose downstream node is to be reduced is transmitted. At this time, the link cost information notified by the link cost notification means 15 may be added with an identifier indicating that the capacity exceeds the capacity, in addition to the link cost value information. . This restricts the selection as a route, determines the upper limit value of the path cost value, assigns that value, and selects the node whose path cost value is larger than the upper limit of the path cost value as the route It is also possible to prevent the number of downstream nodes from increasing too much by causing each node 10 to perform an operation such as not performing.

  By including information other than such simple numerical values in the link cost information, the link cost value can be propagated in the same manner as the operation of adding and propagating. This approach allows a more appropriate selection when the end node 10 decides which route to select.

  The path cost notifying unit 17 inserts path cost information including information on the path cost value from the node 10 to the node 10 as a packet transmission destination target into a control packet (for example, a Hello packet). Notify neighboring nodes. The calculation of the path cost value is a value obtained by adding the link cost value with the parent node to the path cost value notified from the node 10 selected by the node 10 as the parent node from the contents of the path cost table 16. .

  Therefore, in the example of FIG. 2, when the node 10-3 calculates the path cost value for the node 10-0, the path cost value “1” of the node 10-1 and the link cost value “1” of the node 10-1. 1 ”is added, the path passing through the node 10-1 having the path cost value“ 2 ”, the path cost value“ 2 ”of the node 10-2 and the link cost value“ 1 ”of the node 10-2 are obtained. There are two paths that pass through the node 10-2 that have a path cost value of “3”. In such a case, the path passing through the node 10-1 having a small path cost value is adopted as the path to the node 10-0, and its own path cost value to the node 10-0 is “2”. . At this time, if the link cost information indicates that the capacity of the node has been exceeded, it may be excluded from selection as a route.

  As described above, the path cost notifying unit 17 determines a path cost value, and transmits a path cost information packet including information on the determined path cost value to neighboring nodes. Here, the path cost information to be transmitted may be transmitted individually, but the number of packets to be transmitted may be reduced by transmitting the path cost information together with the packet transmitted by the link cost notifying unit 15. .

(A-2) Operation of the First Embodiment Next, the operation of the wireless communication system 1 of the first embodiment having the above configuration will be described.

  First, it is assumed that each node 10 of the wireless communication system 1 is in the state shown in FIG.

  In FIG. 2, each node transmits a Hello packet, the link cost value of each other has been measured, and the route selection to the node 10-0 has been completed in all the nodes 10 other than the node 10-3. Suppose that

  In the downstream node management means 13 of the node 10-0, the nodes 10-1, 10-4, 10-5, 10-6 exist downstream of the node 10-1, and the nodes 10-2, 10-7 are the nodes. It is assumed that it exists from the received upstream data packet that it exists downstream of 10-2.

  The node 10-3 first exchanges the Hello packet with the neighboring nodes 10-1 and 10-2, and the link cost determining means 11, the link cost table 12, and the link cost notifying means 15 operate to link each link. Calculate the cost value.

  The link cost value between the node 10-3 and the node 10-1 is “1”, and the link cost value between the node 10-3 and the node 10-2 is “1”.

  Next, in the node 10-3, the path cost values of the node 10-1 and the node 10-2 to the node 10-0 by the operations of the path cost table 16 and the path cost notifying unit 17 are “1” and “2”, respectively. ”.

  As a result, in the node 10-3, the route to the node 10-0 can be transmitted with the path cost value “2” via the node 10-1. Since it is possible to transmit via the node 10-2 with the path cost value “3”, it is assumed that the route to be transmitted to the node 10-0 via the node 10-1 is selected.

  Thereafter, when the node 10-3 transmits data to the node 10-0, the node 10-3 is added to the downstream node management means 13 of the node 10-0.

  The downstream nodes passing through the node 10-1 are the nodes 10-1, 10-3, 10-4, 10-5, 10-6, and the downstream nodes passing through the node 10-2 are the nodes 10-2, 10-6. -7. In this case, the load balance determining unit 14 adds the value of the link cost of the node 10-1 as a result of the link cost notifying unit 15 so as to adjust the number of downstream nodes to be equal.

  FIG. 3 is an explanatory diagram showing a state of the wireless communication system 1 after the link cost is adjusted by the link cost notifying unit 15 of the node 10-0.

  For example, in the link cost notifying unit 15 of the node 10-0, if “5” is added to the link cost value of the node 10-1, the path cost value of the node 10-1 is “6” as shown in FIG. In the node 10-3, the path cost value passing through the node 10-1 is “7”. Therefore, the node 10-3 switches to a route that passes through the node 10-2.

  In FIG. 3, as an example, the link cost notifying unit 15 of the node 10-0 shows an example of adding “5” to the link cost value of the node 10-1, but this added value is not limited. It is. In the link cost notifying means 15 of the node 10-0, a fixed value set in advance as shown in FIG. 3 may be set as a value to be added to the link cost value, or a child node (node) of the node 10-0 A value corresponding to the difference in the number of downstream nodes 10-1 and 10-2) may be added. Further, in the link cost notifying means 15 of the node 10-0, until the number of downstream nodes of the node 10-1 and the number of downstream nodes of the node 10-2 become equal (or until the difference becomes a predetermined number or less), You may make it add the link cost value with respect to 10-1 sequentially. Then, after the load balance determining means 14 of the node 10-0 once adjusts the link cost value of the node 10-1, this time, the node 10-2 has more downstream nodes than the node 10-1. In the case where the link cost has been lost, it may be determined that the link cost value is adjusted to reduce the number of downstream nodes of the node 10-2.

  By operating as described above, in the wireless communication system 1, the number of downstream nodes of the node 10-1 and the number of downstream nodes of the node 10-2 converge in a direction that is equalized.

(A-3) Effects of First Embodiment According to the first embodiment, the following effects can be achieved.

  In the wireless communication system 1, each node 10 can suppress the concentration of relay traffic on a specific node 10 by adjusting the link cost value, thereby configuring a more optimal wireless multi-hop network. it can.

(B) Second Embodiment Hereinafter, a second embodiment of a node and a wireless communication system according to the present invention will be described in detail with reference to the drawings.

(B-1) Configuration of Second Embodiment FIG. 4 is a block diagram showing an overall configuration of a wireless communication system 1A of the second embodiment.

  In the wireless communication system 1A of the second embodiment, the node 10 of the wireless communication system 1 of the first embodiment is simply replaced with the node 10A. Hereinafter, differences between the wireless communication system 1A of the second embodiment and the first embodiment will be described.

  FIG. 5 is a block diagram illustrating a functional configuration of the wireless node 10A according to the second embodiment.

  In the second embodiment, the link cost notification unit 15 and the path cost notification unit 17 of the node 10 of the first embodiment are replaced with a link cost notification unit 15A and a path cost notification unit 17A, respectively. The wireless communication system 1A is different from the first embodiment in that the path cost notification unit 17A notifies the neighboring nodes of the path cost information reflecting the processing result of the load balance determination unit 14, but the other configuration Since this is the same as in the first embodiment, detailed description thereof is omitted. Note that, unlike the first embodiment, the link cost notification unit 15A does not reflect the processing result of the load balance determination unit 14, and the link cost is not adjusted.

  The path cost notifying unit 17A notifies the neighboring node of the path cost information from the node 10A to the target node 10A of the packet transmission destination. The path cost value of the path cost information notified by the path cost notifying unit 17A is calculated from the contents of the path cost table 16 to the path cost value of the path cost information notified from the node 10 selected by the node 10 as the parent node. The link cost value with the parent node is added, and the value based on the notification from the load balance determination unit 14 is added.

  Then, the path cost notifying unit 17A transmits a path cost information packet including information on the determined path cost value to the neighboring nodes. Therefore, the path cost value of the node 10A needs to be notified of a different value for each neighboring node to be transmitted.

  In the first embodiment, the node 10-0 has been able to broadcast that the path cost for itself is “0”, but in the second embodiment, the path cost information to be notified for each child node. Since the contents of are different, it may be notified individually by unicast.

(B-2) Operation | movement of 2nd Embodiment Next, operation | movement of 1 A of radio | wireless communications systems of 2nd Embodiment which has the above structures is demonstrated.

  First, it is assumed that each node 10A of the wireless communication system 1A is in the state shown in FIG.

  In FIG. 4, each node 10A transmits a Hello packet, the link cost values of each other have been measured, and the route selection to the node 10A-0 is completed in all the nodes 10A other than the node 10A-3. It is assumed that it is in a state.

  The operation of the node 10A-3 here is the same as the operation description of the first embodiment described above until the route to the node 10A-0 is first determined to be via the node 10A-1. .

  After that, when the node 10A-3 transmits data to the node 10A-0, the node 10A-3 is added to the downstream node management unit 13 of the node 10A-0.

  The downstream nodes passing through the node 10A-1 are the nodes 10A-1, 10A-3, 10A-4, 10A-5, 10A-6, and the downstream nodes passing through the node 10A-2 are the nodes 10A-2, 10A-. 7 In this case, the load balance determination unit 14 of the node 10A-0 adds a predetermined value to the path cost value determined by the path cost notification unit 17A so as to adjust the number of downstream nodes to be equal.

  FIG. 6 is an explanatory diagram showing a state of the wireless communication system 1A after the path cost is adjusted by the path cost notifying unit 17A of the node 10A-0.

  In FIG. 6, as an example, when adding “5” in the node 10A-0 to reduce the downstream nodes passing through the node 10A-1, the path cost value “5” is notified to the node 10A-1. Then, the node 10A-2 is notified of the path cost value “0” as before. Then, as illustrated in FIG. 6, the path cost value of the node 10A-1 is “6”, and the path cost value of the node 10A-3 via the node 10A-1 is “7”. Therefore, the node 10A-3 switches to a route that passes through the node 10A-2.

  FIG. 6 shows an example in which “5” is added to the path cost value notified to the node 10A-1 in the path cost notification unit 17A of the node 10A-0. However, the value to be added is not limited. Is. The path cost notifying unit 17A of the node 10A-0 may set a preset fixed value as shown in FIG. 6 as a value to be added to the path cost value, or may be a child node (node) of the node 10A-0 A value corresponding to the difference in the number of downstream nodes 10A-1, 10A-2) may be added. Further, in the path cost notifying unit 17A of the node 10A-0, until the number of downstream nodes of the node 10A-1 and the number of downstream nodes of the node 10A-2 become equal (or until the difference becomes a predetermined number or less), You may make it add the path cost value notified to 10A-1 sequentially. Then, after the load balance determination means 14 of the node 10A-0 once adjusts the path cost value of the node 10A-1, this time, the node 10A-2 has more downstream nodes than the node 10A-1. In the case where it has been, the decision may be made to adjust the path cost value notified to reduce the number of downstream nodes of the node 10A-2.

  By operating as described above, in the wireless communication system 1A, the number of downstream nodes of the node 10A-1 and the number of downstream nodes of the node 10A-2 converge in a direction that is equalized.

(B-3) Effects of Second Embodiment According to the second embodiment, the following effects can be achieved.

  In the wireless communication system 1, by adjusting the path cost value notified to each child node by each node 10A, it is possible to suppress the concentration of relay traffic on the specific node 10A. A network can be configured.

(C) Other Embodiments The present invention is not limited to the above-described embodiments, and may include modified embodiments as exemplified below.

(C-1) In each of the above embodiments, all the nodes constituting the wireless communication system have been described as nodes of the present invention. However, only a part of the present invention node is applied, and other nodes of the present invention You may make it apply the node of a different structure from a node.

  For example, the node of the present invention may be applied only to a node that is a parent node of a node where concentration of relay traffic is expected. For example, in the example of FIG. 1, the node of the present invention may be applied only to the node 10-0, and the existing nodes may be applied to the other nodes 10-1 to 10-7.

(C-2) In each of the above embodiments, the transmission destination of the data packet of each node constituting the wireless communication system has been described as being not limited. However, a specific node is a sink node, and other nodes are sinks. A configuration may be adopted in which data is transmitted to the node. For example, in the first embodiment, the node 10-0 may operate as a sink node, and the nodes 10-1 to 10-7 may be configured as sensor nodes that transmit sensor data to the node 10-0.

  DESCRIPTION OF SYMBOLS 1 ... Wireless communication system 10, 10-0 to 10-7 ... Node, 11 ... Link cost determination means, 12 ... Link cost table, 13 ... Downstream node management means, 14 ... Load balance determination means, 15 ... Link cost notification Means, 16 ... path cost table, 17 ... path cost notifying means.

Claims (5)

In a node that performs multi-hop wireless communication,
A neighboring node capable of direct wireless communication, control information transmission / reception means for transmitting / receiving a control packet having control information,
Link cost calculation means for calculating a link cost value of a link with each neighboring node according to the status of control information transmission / reception by the control information transmission / reception means,
Path cost calculation means for calculating a path cost value until reaching the target node when transmitting a packet to the target node;
Downstream node monitoring means for monitoring the number of downstream nodes for each of the child nodes of the node on the path to reach the target node;
Control information to be transmitted by the control information transmission / reception means, wherein the control information to be created includes link cost information based on the link cost value calculated by the link cost calculation means and / or the path cost calculation means. The path cost information based on the calculated path cost value is inserted, and the contents of the link cost information or the path cost information to be inserted into the control information to be created are adjusted according to the number of downstream nodes of each child node. And a control information creating means for adjusting the number of downstream nodes of each child node.   The node according to claim 1, wherein the downstream node monitoring unit grasps the number of downstream nodes of each child node by referring to the contents of a packet received by the node from a neighboring node.   The control information creation means adjusts the link cost value with each child node included in the link cost information to be created according to the number of downstream nodes of each child node, thereby downstream nodes of each child node. The node according to claim 1, wherein the number is adjusted.   The control information creating means creates different control information for each child node, and in accordance with the number of downstream nodes of each child node, the node of the path cost information to be inserted into the control information for each child node 3. The node according to claim 1, wherein the number of downstream nodes of each child node is adjusted by adjusting a path cost value targeted for.   In a wireless communication system having a plurality of nodes performing multi-hop wireless communication, the node according to any one of claims 1 to 4 is applied to a part or all of the nodes constituting the wireless communication system, Wireless communication system.

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